By Liz Stephens

The prime minister has congratulated US president Barack Obama on winning the Nobel peace prize today.

A Downing Street spokesman told politics.co.uk: “The prime minister has sent a private message of congratulations.”

However, Downing Street would not be drawn on the content of the message.

Mr Obama was awarded the prize “for his extraordinary efforts to strengthen international diplomacy and co-operation between peoples” and for his work on nuclear non-proliferation.

A statement by the Nobel committee said: “The committee endorses Obama’s appeal that ‘now is the time for all of us to take our share of responsibility for a global response to global challenges’.”

The award stunned those present at the ceremony and pundits around the world as Mr Obama has only been in office for 10 months.

The president was not even known to have been on the shortlist.

Nobel committee chairman, Thorbjoern Jagland, said: “Only rarely has a person such as Obama captured the world’s attention and given his people hope for a better future.”

While Mr Brown was reticent to praise Mr Obama in public, German chancellor Angela Merkel had no such qualms, publicly congratulating the US president.

“In a short time he has been able to set a new tone throughout the world and to create a readiness for dialogue,” Ms Merkel said.

However, Danish foreign minister Stig Moeller referred to the decision to award Mr Obama so early in his political career “an unusual choice”.

Other critics around the world have been less diplomatic, calling the move sensationalist” and “premature”.